It is the night before the Tour de France begins. Twenty-three men climb on board a bus in the car park of the Hotel Golfe in Porto Vecchio, Corsica. The bus will not move until the next morning but for those filling the seats, standing in the aisle, the journey has already begun. At the front of the Team Sky bus, facing the other 22, stands Sir Dave Brailsford.

Though the team are starting only their fourth Tour de France this eve-of-battle meeting of staff members has already become a tradition. There is laughter and jibing as relative latecomers try to beat the digital clock at the front of the bus: 8.55 ... 8.56 ... 8.57 ... who will be late? No one.

Brailsford knows the importance of such moments. As 8.59 changes to 9.00, the din of bonhomie fades to expectant silence. The team principal takes out his iPhone and says he wants to take a photograph of everyone on the bus. "Now the question I want you to consider is what memories this photo will evoke when you look at it six months from now.

"You will want to say these were the best group of people I ever worked with, as good as any team could have had. You'll want to look back and say we were good on that Tour."

I sit in the seat of the Belarus rider Kosta Siutsou, listen to Brailsford and recall Henry V and his eve-of-battle speech: And gentlemen in England nowa-bed Shall think themselves accurs'd they were not here.

For three weeks this group of people will work together, trying to ensure Sky's nine riders are the best-supported in the race. Arriving at the team hotel each evening, their cases already in their rooms, they will find the carer Mario Pafundi waiting to greet them. Pafundi is neatly built, black hair, Mediterranean good looks, natural charm and an astonishing memory.

Every day he is first at the hotel, gets the suitcases to all the rooms and then memorises the room numbers of every rider and every staff member. Four hours later they all arrive. "Chris, 214, second floor, key in your room; Edvald, 242, second floor ..." "Mario, Mario, my room?" "402, fourth floor, suitcase is already there."

The team are addicted to detail; pineapple juice to make water more drinkable, every bike checked and passed by two mechanics, riders before staff in the restaurant and when the next day's plan is distributed in the evening, you read it and think they could invade China.

And then, on the stage to Alpe d'Huez, things went haywire.

Marko Dzalo and David Rozman, two Slovenian carers, filled the big cooler box in the team car with ice the night before, thinking that for such a big day they needed to be ahead of themselves. In the morning, they topped up with one more bag of ice. But the previous evening's ice had begun to melt and on the descent from the Col d'Ornon, 15km before the first of two ascents of Alpe d'Huez, mechanic Gary Blem, sitting in the back of the team car, heard water sloshing about in the cooler. Unknown to him, the water was escaping and dripping into the electronics of the Jaguar.

This was the number one team car, driven by the director sportif, Nicolas Portal, and detailed to take care of Chris Froome. After the first climb, the dashboard panel had flashing warning lights everywhere.

Blem reached back and saw the water all over the boot, causing the electrical carnage that foretold the day's disaster.

On the descent from the Col de Sarenne, 20km before the second climb of Alpe d'Huez, the car cut out. Blem coaxed the battery into renewed life but that lasted only a few minutes.

They waited on the side of the road for the second team car to come, seven minutes that seemed like eternity, then they switched cars and tried to recover their number one place in the cavalcade.

It was close to hopeless, for by now the leaders were climbing Alpe d'Huez for a second time and, on a road filled with fans, overtaking was dangerous and difficult. Needing to feed before Alpe d'Huez, Froome got teammate Pete Kennaugh to go back to the team car. "Car's not there," said Kennaugh on his return.

At this point Portal was too far from Froome for their two-way radio to work. Having missed an opportunity to refuel, the race leader was becoming hypoglycemic; that is extremely low on sugar. Seven kilometres from the summit, Portal had worked his way through some of the race cars when he heard Froome's voice on the radio. "Nico, sugar, sugar, I need sugar." Portal still had some overtaking to do and by the time he was in position behind Froome, it was too late legally to give the rider the sugar-rich gels he sought.

Still it had to be done; Porte dropped back, got the gels, passed them to Froome and the race leader would lose just 69 seconds to Nairo Quintana.

Because Alberto Contador had a bad day, Froome increased his lead in the race to more than five minutes. That evening Neil Thompson, the Jaguar mechanic Brailsford has had with the team on the Tour, worked on the broken car from 6pm to midnight.

This is Thompson's second Tour with Sky. Before this, he had no interest in cycling. Football is probably his game. He manages his son's team and when he says they went through last season without winning, he wants you to understand he could never see sport as a matter of life and death. But this car, he badly wanted it back on the road. Thought he had it, all those flashing lights went away, but then late in the night, a warning light for the air-suspension system triggered and he knew he was struggling. He went to bed worried, woke up worried; and when he went to the car first thing in the morning, he threw up, anxiety churning away until his stomach could take no more. "I know it shouldn't matter so much but I want this team to win. We needed the car back in the race and now I'm probably going to have to pull it out."

THIS evening in Paris, Froome will pull on his final Yellow Jersey and be acclaimed the winner of the Centenary Tour de France. He becomes the first African to win the Tour, after a race in which he has excelled and been accused of doping solely because he has been so good. Though many spectators have cheered, plenty have booed. Broken is the trust between athlete and fan.

Six months ago I spent a week with Team Sky at a training camp in Majorca, the start of a project that would involve my living "inside" the team. Tomorrow night I will say goodbye to people with whom I've shared nine weeks since that trip. There was a week in Tenerife, another trip to Majorca, two days in Nice, two weeks at the Giro d'Italia, almost four weeks at Le Tour.

The objective was straightforward: to determine as much as I could what was the culture inside the team, to see if they were ethical and free of doping.

Because Froome was likely to be the team's star rider, he was the one I most wanted to know.

On the second rest day at the Giro d'Italia, I meet Richard Freeman, the team doctor, at a cafe in Bardonecchia. Freeman's background is football, working for Bolton in the Premier League before accepting an offer from the British track cycling team and Team Sky. We have a coffee, go for a walk, talk for two hours and along the way he describes his reaction to Froome's breakthrough performance at the 2011 Vuelta a Espana.

He knew Froome as a rider with great talent but whose good days were followed by bad ones. Then, at that Vuelta, three weeks, not one bad day and second place overall.

At first Freeman wasn't convinced.

"I was confused because Chris hadn't performed with this consistency for the team and I wondered how he'd done it. Before I could be satisfied, I spent two weeks re-examining all of his blood samples from his two seasons in our team and looked at all the information in his biological passport.

"What I wanted was to compare blood results from the Vuelta with the blood tests he'd done previously to see if there were changes. There weren't. His blood values remained the same and whatever the reasons for him riding consistently in that Vuelta, in my opinion it wasn't down to him doing things he shouldn't have done." Freeman's admission of initial concern was reassuring.

His desire to investigate even more so.

Brailsford believes that Froome's progress in 2011 was in part related to his successfully managing his bilharzia, a debilitating condition caused by a parasite that attacks red cells. The rider himself also believed that as he gained experience, he raced more intelligently. But who was he? How could a kid from a suburb south of Nairobi in Kenya get to the top of Mont Ventoux quicker than every other rider in the Tour de France.

Picture him in 2006, a 21-year-old economics student at the University of Johannesburg, desperate to ride in the under-23 world championships in Salzburg. Kenya wasn't organised or interested in that event. So he arranged his travel and equipment, acting as manager to a team in which he was the only competitor.

He rode to the manager's meeting in Salzburg but in the rain couldn't find the venue. Twenty minutes late, he walked into the room with his bike under his arm. "This is a managers' meeting," someone said, "not for riders." By now there was a pool of water by his feet. "I am a manager," he said and everyone in that room with half a brain knew this kid had something about him.

Think of him seven months later at the Giro delle Regioni, his second visit to Europe and first stage race in the old continent.

Europe. "I got over to Regioni, third day was a mountain top finish, and I was surprised how easily I rode away from the leaders going up the last climb, I was with a Russian and a Slovenian. We dropped the Russian. The Slovenian was on my wheel and he begged me to slow down, saying he would give me the stage, 'Just don't drop me, don't drop me'. 'OK, OK', I said, 'not a problem'. We got to the last hairpin and they pulled the front vehicles off, into a 'derivation'. I followed the vehicles off the course and as this was 100m before the finish line the Slovenian won the stage. I had to do a bit of a U-turn there.

"Two days later we had another uphill finish in Montepulciano and I didn't wait for anyone there, just went on my own, 5km from the finish, up through cobbled roads. It was beautiful, my first win in Europe. I was blown away."

Froome might have won that six-day race if only he had known how to ride his bike. "I had never done a descent before, not a proper descent with switchbacks. The descents I'd done in Africa were pretty straight, I never had to ride a technical descent and didn't realise I had to use my front brake. I always thought that if I pulled my front brake, I would go over the bars. Using the back brake on the descents, I kept crashing. I wrote off three bikes that week, lost a trunk of time."

Geraint Thomas, Ian Stannard and Ben Swift, now his teammates at Sky, all rode the Giro delle Regioni that year. They couldn't get near him on the climbs. On the descents, they tried to stay well clear.

MIDWAY through this Tour de France, I asked Sky's chief doctor, Alan Farrell, about therapeutic use exemptions (TUEs) which, traditionally, have been one route taken by cyclists seeking unethical advantage. They claim a medical reason for needing a banned corticosteroid, persuade the team doctor to apply for it and try to beat the system that way.

"I've been with the team since April last year, almost 16 months. Applications for TUEs come from me and in my time, we have applied for two TUEs."

Farrell was at a medical practice in Dublin before joining Sky. On Thursday he travelled in a team car up Alpe d'Huez and felt as much under siege as every Sky car in the race cavalcade.

Eggs smashed against the cars, beer too, and when a car slowed enough for the jeering mob to rock it from side to side, that's what they did. The abuse was worst at those parts of the climb populated by Irish and Dutch fans. "Froome Dope" was one of the bigger signs at the Irish corner. All the way up to the top there were fans screaming at Sky riders while mimicking the act of injecting into their arms.

Two young men ran beside Froome, each with a "toy" giant syringe filled with an unknown substance. One got close, pressed the plunger and sprayed the substance directly into his face. The leader instinctively struck out with his right arm and punched the guy in the face, an act of physical violence utterly at odds with his character. "Some of the stuff went into my mouth, it might have been beer but I was conscious of not wanting to swallow even a drop and just kept spitting out. I was thinking, 'What if there's some product in that stuff'."

The ascents of Alpe d'Huez scared him. "Once there were riots in Kenya and my mum and I got stopped going through a particularly dangerous township. The protesters rocked our car, we didn't know what was going to happen. Alpe d'Huez reminded me of that day."

Farrell met some Irish fans the next morning in Bourg d'Oisans and told his compatriots how disappointed he'd been by the reaction to Froome and Sky. "Our team is doing this sport in the right way," he said, "and that's what we get from you guys." There were tears in his eyes as he spoke.

A little later, four cyclists from Lakeside Cycling Club in Mullingar found Brailsford and told him they were sorry. A Dutch journalist told me he was shamed by the behaviour of his compatriots.

Through it all, Froome has been a beacon of calmness. When Portal suggested appealing against Froome's 20-second penalty for taking that feed on Alpe d'Huez, the leader advised him not to. "Nico, if I hadn't got the gels at that point, I could have lost two minutes. Twenty seconds is OK." This has been a terrific Tour de France and it has delivered a great new champion, one who started out in Kenya's Ngong hills and learnt to love the bike while riding with a group of black friends. It was his good fortune to enter the sport when anti-doping controls were becoming more effective and attitudes changing. As for the mob reaction on Thursday, it was a reminder of how Lance Armstrong was regarded. Once he was the most loved sportsman on the planet. Partly because of that betrayal, the mob was baying for Froome's blood on the Alpe. They were wrong when Armstrong was winning. And they are wrong now about Froome.

History will correct this, as it did the Armstrong story.